The present invention relates to disposable absorbent underpants and more particularly to such underpants provided in the form of completely assembled underpants to be used, for example, as training pants for babies or underpants for incontinents.
The disposable absorbent underpants provided in the form of completely assembled underpants and containing elastic members in the waist band and a pair of leg-holes, respectively, has already been disclosed by Japanese Unexamined Patent Publication No. 58-11507. The underpants constructed in accordance with this prior art comprise the laterally elongate rectangular water-permeable topsheet dimensioned to form the front and rear areas, the water-impermeable backsheet identical to said topsheet both in the shape and the dimension, the absorbent cores sandwiched between these sheets leaving the central area defined midway between the laterally opposite ends of said sheets as the blank space so as to associate the respective absorbent cores with the front and rear areas, the elastic member adhesively fixed onto the backsheet along the upper end thereof so as to associate this elastic member with the waist band and the elastic member similarly fixed onto the backsheet along the lower end thereof so as to associate the elastic member with the respective leg-holes. The main body of underpants thus constructed is folded back along the central line of said blank area, then the front and rear area are joined together along the side edges thereof which are opposite to said blank area and finally the front and rear area are joined along the lower end of the central area defined between said side edges and the other side edge formed by folding back said blank area to form completely assembled underpants
The underpants of said prior art is certainly advantageous in that the manufacturing thereof is simplified but involve various inconveniences such that the function of absorption is inadequate since the components of the front and rear areas to be joined together are concentrated in the crotch area; these components are disjoined or broken, resulting in loss of the desired function as the underpants and leakage of excretions since the crotch area is subjected to the highest tensile force due to movement of the wearer's legs; and said components give the wearer feelings of uncomfortable incompatibility. In addition, the front and rear areas are identically dimensioned, so that the area corresponding to hip is placed under a tension (i.e., becomes "tight") while the area corresponding to belly slackens (i.e., becomes "loose") due to rigidity of the components of underpants, particularly of the absorbent cores and the figure of human body (baby).
Furthermore, with the underpants of said prior art, said elastic members are sandwiched between said topsheet and said backsheet as extending substantially over the width of said cores or slightly beyond the length thereof, so said elastic members, particularly those associated with said respective leg-holes which are important to prevent excretions from leakage around the crotch hardly have their portions being capable of elastically functioning without any adverse influence of the rigidity inherent in said cores and, with a consequence, a sealing effect of said leg-holes is unsufficient to avoid leakage of excretions. Additionally, when said joining is effected by welding, the portions thus joined together will become stiffer relative to the remaining portions and give the wearer pain or even injury as a result of contact of said joined portions with the wearer's skin, since no particular care is not paid for such manner of joining.
Moreover, as the underpants in which the waist band portions associated with the front and rear areas, respectively, are connected into the annular band, it is impossible to adjust an overlapping width of the laterally opposite sides of the front and rear areas and a tightness of the area adjacent and inclusive of the waist band, this being possible with the disposable diaper of open type in which said waist band portions are connected by tape fastener in actual use of the diaper. As a further inconvenience, wrinkles due to slackening are formed in the area adjacent the lower edge of the waist band in the front area when the underpants are actually worn, since the components of the underpants are more rigid than those of the fabric diaper and baby's belly generally projects forwards.
The object of the present invention is, therefore, to provide improved disposable absorbent underpants adapted to overcome the drawbacks as have been set forth hereinabove by most simple measures.